Critical Reasoning: Conclusion Weakening Questions

To which Critical Reasoning question type does the following question stem belong?

"Which of the following, if true, casts the most doubt on the argument's conclusion?"

You're right!

Incorrect. The question stem of Assumption questions usually includes the word assumption or a similar word. 

Incorrect. The question stem of Paradox questions usually includes the word paradox or discrepancy.

Incorrect. The question stem of Conclusion Strengthening questions usually includes the word strengthen or support.